1. Field of Invention
The present invention relates to switchgear including switching and interrupting devices and their combination such as circuit breakers, transfer switches, combination circuit breakers and transfer switches, recloser apparatus and similar devices as used in connection with the generation, transmission, distribution and conversion of electric power.
2. Discussion of Prior Art
Present switchgear such as circuit breakers employ various means to extinguish the arc generated upon contactor opening under fault conditions. The behavior of switchgear is dependent on the current broken and the arc energy. Present techniques for arc extinction include; increasing the arc length, cooling the arc and splitting the arc into a number of series arcs. Methods to achieve the above include arc chutes of both the insulated plate and cold cathode types. The arc is resilient and can be stretched, and possesses resistance which can be increased by lengthening and by confinement. When the voltage drop across the arc equals the driving voltage, the arc is extinguished. Power arcs can evade deionization systems by swerving, by striking out in new and unexpected directions, and by reigniting after they appear to have been successfully extinguished. All present circuit breakers interrupt current shortly before a current zero due to arc instability at low currents.